The present invention generally involves a fill system and method for dispensing a liquid containing a chemical into a canister containing materials that absorb, adsorb, and/or react with the chemical.
Materials within the scope of this invention include, for example, sanitary wipes, facial towels, baby wipes, and any other pre-moistened materials packaged in canisters. The materials are typically made of woven or non-woven fabric that exhibits absorbent and/or adsorbent characteristics. In lieu of adsorbent characteristics, or in addition thereto, the materials may include a reactant that can react with the chemical. As used herein, the term “woven” refers to a fabric composed of individual fibers or filaments which are interlaid in an identifiable repeating pattern, and the term “non-woven” refers to a fabric composed of randomly or non-repeating patterns of interlaid fibers or filaments.
Chemicals within the scope of this invention include, for example, active ingredients, biocides, preserving agents, surfactants, cleaning agents, and any other elements that are capable of adsorption and/or reaction with the materials. The chemicals generally exist in solution or suspension and are applied to the materials during manufacture and packaging.
The materials may be individual or perforated sheets that are stacked or rolled during manufacture and placed in a canister having an open fill side. For uniformity, the container will be generically referred to as a canister, although other types of containers, such as bags, sacks, bottles, and similar carriers are within the scope of the present invention. The canister passes through a conventional fill system designed to add liquid containing the chemical to the canister.
The conventional fill system dispenses the liquid through the open fill side into the canister containing the materials. The fill system dispenses the liquid in a column or spray of fluid, typically at a discrete location such as the center of the open fill side. Once the canisters are filled with sufficient liquid containing the chemical, a lid or permanent closure is applied to the open fill side of the canister, and absorption, adsorption, and/or reaction processes begin simultaneously, with varying results as will be explained.
The absorption process involves physical entrainment of the liquid in the fibers of the materials. Absorption occurs through wicking phenomena via the transport of liquid through interstitial spaces within the fibers. The transport of liquid (i.e., the wicking) occurs as the liquid moves from the saturated or filled interstitial spaces within the absorbent material to unsaturated or unfilled interstitial spaces within the absorbent material, without regard to the chemical concentration in the liquid. In fill processes where the liquid is added to the center of the stacked or rolled sheets, the stacked or rolled sheets absorb the liquid from the center of the canister outward to the stacked or rolled sheets at the outer perimeter of the canister. The absorption process generally produces a discernable saturation gradient, “saturation” defined as the weight of the liquid absorbed divided by the weight of the absorbent material, in stacked or rolled materials that is highest where the liquid is added, typically the center of the stacked or rolled material.
The adsorption process involves surface interaction between the chemical and the fiber surfaces of adsorbent materials. For adsorbent materials, the fiber surfaces possess a designed affinity for the chemical. As absorption occurs and the liquid passes radially outward through the fibers, as previously described, the chemical comes into contact with the fiber surfaces, and the fiber surfaces strip or adsorb the chemical from the liquid. The fiber surfaces continue to strip or adsorb the chemical from the liquid until an equilibrium condition exists between the chemical concentration on the fiber surfaces and the chemical concentration in the liquid. As absorption continues, the remaining chemical that has not been adsorbed continues to migrate radially outward with the liquid via the absorption process. This results in progressively lower chemical concentrations being exposed to the outer fibers of the stacked or rolled adsorbent materials, producing a radially outward decreasing chemical concentration gradient in the fibers of the adsorbent materials.
The reaction process, if present, produces a chemical concentration gradient similar to the adsorption process. As previously described, the absorption process transfers the liquid radially outward through the fibers. As this occurs, the chemical reacts with the reactant, removing the chemical from the liquid, and the reduced chemical concentration migrates radially outward via the absorption process. This produces a radially outward decreasing chemical concentration gradient in the materials.
Thus, the absorbent, adsorbent, and/or reaction processes combine to produce two simultaneous effects in the stacked or rolled materials. First, the absorption process produces a discernable saturation gradient in stacked or rolled materials that is highest where the liquid is added, typically the center of the stacked or rolled material. Second, the adsorption and/or reaction processes cause the chemical concentration in the liquid to diminish as the chemical passes radially outward and is progressively adsorbed by or reacts with the materials. As a result, the combination of absorbent and adsorbent and/or reaction processes produce a chemical concentration gradient in the stacked or rolled sheets that is highest at the center and decreases with distance from the center.
The present invention relates to an improved fill system and method for reducing the chemical concentration gradient in materials that absorb, adsorb, and/or react with the chemical.